Structure of the 70 S ribosome: implications for movement

2002 ◽  
Vol 30 (6) ◽  
pp. 1159-1161 ◽  
Author(s):  
H. F. Noller ◽  
A. Baucom
Keyword(s):  
16S Rrna ◽  
Crystal Structures ◽  
Ground State ◽  
Ribosomal Subunit ◽  
Molecular Machine ◽  
Structural Elements ◽  
X Ray ◽  
Functional States ◽  
Moving Parts

The ribosome is a complex molecular machine, with moving parts, many of which are structural elements of rRNA. We compared the X-ray crystal structures of three different functional states of the 30 S ribosomal subunit - two from crystal structures of the isolated 30 S subunit from the Ramakrishnan group and one from a complex of the 70 S ribosome. Even though all three structures are in what could be called the ‘ground state’ of the subunit, many conformational differences are found, distributed over the whole structure. A striking example is the undulating movement of the penultimate stem of 16S rRNA, which forms several intersubunit bridges with the 50 S subunit.

Structural Studies of a Series of Organic Non-Linear Optical Materials

1997 ◽  
Vol 53 (5) ◽  
pp. 812-821 ◽  
Author(s):  
J. C. Cole ◽  
J. M. Cole ◽  
G. H. Cross ◽  
M. Farsari ◽  
J. A. K. Howard ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Ground State ◽  
Optical Materials ◽  
Dipole Moments ◽  
Solvent Polarity ◽  
Structural Studies ◽  
Acta Cryst ◽  
X Ray ◽  
Solution State ◽  
X Ray Crystallography

The crystal structures of {4-[bis(diethylamino)methylium]phenyl}dicyanomethanide (I), {4-[cyano(4-methylpiperidyl)methylium]phenyl } dicyanomethanide (II), {4-[cyano(1-pyrrolidinyl)methylium]phenyl}dicyanomethanide (IV) and (Z)-{4-[1,3-dicyano-3-(diethylamino)-2-propenylium]phenyl} dicyanomethanide have been determined by X-ray crystallography. Together with (Z)-{4-[1-cyano-3-(diethylamino)-2-propenylium]phenyl}dicyanomethanide [(III): Cole, J. C., Howard, J. A. K., Cross, G. H. & Szablewski, M. (1995). Acta Cryst. C51, 715–718], these compounds exhibit varying degrees of quinoidal characteristics and yet have predominantly zwitterionic ground state character. The presence of high dipole moments in the crystal can thus be inferred and are substantiated by measurements of high solution-state dipole moments. Negative solvatochromism (hypsochromism on increasing solvent polarity) confirms the zwitterionic character in at least two of the series.

scholarly journals Structures of TOG1 and TOG2 From the Human Microtubule Dynamics Regulator CLASP1

2018 ◽  
Author(s):  
Jonathan B. Leano ◽  
Kevin C. Slep
Keyword(s):  
Crystal Structures ◽  
Family Members ◽  
Structural Diversity ◽  
Binding Activity ◽  
Structure And Function ◽  
Microtubule Dynamics ◽  
Structural Elements ◽  
X Ray ◽  
Tubulin Binding ◽  
And Function

AbstractTubulin-binding TOG domains are found arrayed in a number of proteins that regulate microtubule dynamics. While much is known about the structure and function of TOG domains in the XMAP215 microtubule polymerase family, less in known about the TOG domain array found in the CLASP family. The CLASP TOG array promotes microtubule pause, potentiates rescue, and limits catastrophe. How distinct the TOG domains of CLASP are from one another, from XMAP215 TOG domains, and whether they are positionally conserved across CLASP family members is poorly understood. We present the x-ray crystal structures of human CLASP1 TOG1 and TOG2. The structures of CLASP1 TOG1 and TOG2 are distinct from each other, from CLASP TOG3, and are positionally conserved across species. While studies have failed to detect CLASP TOG1 tubulin-binding activity, TOG1 is structurally similar to the free-tubulin binding TOG domains of XMAP215. In contrast, though CLASP TOG2 and TOG3 have tubulin binding activity, they are structurally distinct from the free-tubulin binding TOG domains of XMAP215. CLASP TOG2 has a convex architecture, predicted to engage a hyper-curved tubulin state. CLASP TOG3 has unique structural elements in the C-terminal half of its α-solenoid domain that modeling studies implicate in binding to laterally-associated tubulin subunits in the microtubule lattice in a mode similar to, yet distinct from XMAP215 TOG4. These findings highlight the structural diversity of TOG domains within the CLASP TOG array and provide a molecular foundation for understanding CLASP-dependent effects on microtubule dynamics.

Transmission electron microscope studies in special ceramics

1978 ◽  
Vol 36 (1) ◽  
pp. 268-269
Author(s):  
A. Zangvil ◽  
L.J. Gauckler ◽  
G. Schneider ◽  
M. Rühle
Keyword(s):  
Phase Diagrams ◽  
Crystal Structures ◽  
Thin Foil ◽  
Limited Extent ◽  
Complex Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Lattice Resolution

The use of high temperature special ceramics which are usually complex materials based on oxides, nitrides, carbides and borides of silicon and aluminum, is critically dependent on their thermomechanical and other physical properties. The investigations of the phase diagrams, crystal structures and microstructural features are essential for better understanding of the macro-properties. Phase diagrams and crystal structures have been studied mainly by X-ray diffraction (XRD). Transmission electron microscopy (TEM) has contributed to this field to a very limited extent; it has been used more extensively in the study of microstructure, phase transformations and lattice defects. Often only TEM can give solutions to numerous problems in the above fields, since the various phases exist in extremely fine grains and subgrain structures; single crystals of appreciable size are often not available. Examples with some of our experimental results from two multicomponent systems are presented here. The standard ion thinning technique was used for the preparation of thin foil samples, which were then investigated with JEOL 200A and Siemens ELMISKOP 102 (for the lattice resolution work) electron microscopes.

Microchemical imaging in biomedical research

1992 ◽  
Vol 50 (2) ◽  
pp. 1118-1119
Author(s):  
P. Ingram
Keyword(s):  
Data Analysis ◽  
Electron Probe ◽  
The Other ◽  
X Ray ◽  
Cell Element ◽  
Physiological Information ◽  
Functional States ◽  
Elemental Maps ◽  
Electron Energy Loss ◽  
Secondary Ion

It is well established that unique physiological information can be obtained by rapidly freezing cells in various functional states and analyzing the cell element content and distribution by electron probe x-ray microanalysis. (The other techniques of microanalysis that are amenable to imaging, such as electron energy loss spectroscopy, secondary ion mass spectroscopy, particle induced x-ray emission etc., are not addressed in this tutorial.) However, the usual processes of data acquisition are labor intensive and lengthy, requiring that x-ray counts be collected from individually selected regions of each cell in question and that data analysis be performed subsequent to data collection. A judicious combination of quantitative elemental maps and static raster probes adds not only an additional overall perception of what is occurring during a particular biological manipulation or event, but substantially increases data productivity. Recent advances in microcomputer instrumentation and software have made readily feasible the acquisition and processing of digital quantitative x-ray maps of one to several cells.

Protein-induced conformational changes in 16S rRNA during assembly of the Escherichia Coli 30S ribosomal subunit: A STEM study

1987 ◽  
Vol 45 ◽  
pp. 910-911
Author(s):  
M. Boublik ◽  
V. Mandiyan ◽  
J.F. Hainfeld ◽  
J.S. Wall
Keyword(s):  
16S Rrna ◽  
Conformational Changes ◽  
Ribosomal Proteins ◽  
Structural Changes ◽  
Ribosomal Subunit ◽  
Compact Structure ◽  
E Coli ◽  
Freeze Dried ◽  
16S Rna ◽  
30S Subunit

The aim of this study is to understand the mechanism of 16S rRNA folding into the compact structure of the small 30S subunit of E. coli ribosome. The assembly of the 30S E. coli ribosomal subunit is a sequence of specific interactions of 16S rRNA with 21 ribosomal proteins (S1-S21). Using dedicated high resolution STEM we have monitored structural changes induced in 16S rRNA by the proteins S4, S8, S15 and S20 which are involved in the initial steps of 30S subunit assembly. S4 is the first protein to bind directly and stoichiometrically to 16S rRNA. Direct binding also occurs individually between 16S RNA and S8 and S15. However, binding of S20 requires the presence of S4 and S8. The RNA-protein complexes are prepared by the standard reconstitution procedure, dialyzed against 60 mM KCl, 2 mM Mg(OAc)2, 10 mM-Hepes-KOH pH 7.5 (Buffer A), freeze-dried and observed unstained in dark field at -160°.

Crystal Structures of Fragments D and Double-D from Fibrinogen and Fibrin

1999 ◽  
Vol 82 (08) ◽  
pp. 271-276 ◽  
Author(s):  
Glen Spraggon ◽  
Stephen Everse ◽  
Russell Doolittle
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Crystal Structures ◽  
Structure And Function ◽  
X Ray ◽  
Long Period ◽  
And Function

IntroductionAfter a long period of anticipation,1 the last two years have witnessed the first high-resolution x-ray structures of fragments from fibrinogen and fibrin.2-7 The results confirmed many aspects of fibrinogen structure and function that had previously been inferred from electron microscopy and biochemistry and revealed some unexpected features. Several matters have remained stubbornly unsettled, however, and much more work remains to be done. Here, we review several of the most significant findings that have accompanied the new x-ray structures and discuss some of the problems of the fibrinogen-fibrin conversion that remain unresolved. * Abbreviations: GPR—Gly-Pro-Arg-derivatives; GPRPam—Gly-Pro-Arg-Pro-amide; GHRPam—Gly-His-Arg-Pro-amide

Synthesis of Sulfoquinovose and Sulfoquinovosyl Diacylglycerides, and a Fluorogenic Substrate for Sulfoquinovosidases

2019 ◽  
Author(s):  
Yunyang Zhang ◽  
Janice Mui ◽  
Thimali Arumaperuma ◽  
James P. Lingford ◽  
ETHAN GODDARD-BORGER ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Fluorogenic Substrate ◽  
Potassium Salts ◽  
X Ray ◽  
Sulfoquinovosyl Diacylglycerol ◽  
Sodium And Potassium

<p>The sulfolipid sulfoquinovosyl diacylglycerol (SQDG) and its headgroup, the sulfosugar sulfoquinovose (SQ), are estimated to harbour up to half of all organosulfur in the biosphere. SQ is liberated from SQDG and related glycosides by the action of sulfoquinovosidases (SQases). We report a 10-step synthesis of SQDG that we apply to the preparation of saturated and unsaturated lipoforms. We also report an expeditious synthesis of SQ and (<sup>13</sup>C<sub>6</sub>)SQ, and X-ray crystal structures of sodium and potassium salts of SQ. Finally, we report the synthesis of a fluorogenic SQase substrate, methylumbelliferyl a-D-sulfoquinovoside, and examination of its cleavage kinetics by two recombinant SQases.</p>

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